Resistor and method of making same



JunelS, 1929 s, o w' 1,717,712

REsfs'roR AND METHOD OF MAKING SAME Filed Jan. 17, 1927 INVENTOR SIEGMUND, LOEWE wig ATTORNEY Patented June 18, 1929.

smemmn town, or BERLIN,

FRIEDE'NAU, GERMANY, ASSIGNOB TO RADIO COR- OBATION OF AMERICA, A CORPORATION OF DELAWARE.

RESISTOR AN D METHOD OF MAKING SAME.

Application filed January 17,

This invention relates to resistors and more particularly to resistors of such a type as are used, for example, for grid leaks, where a high stable resistance is desirable.

Special kinds of highbhmic resistances were heretofore customarily made by applying a surface layer or film upon an insulating carrier or support, for example, by

squirting or spraying thereon carbonor graphite-containing solutions. Resrstances so made, on account of the behavior of the carbon, were causative of manufacturing difiiculties. Carbon'being hygroscopic, undergoes alterations of its resistance value even during its manufacturing process. These changes which are due to changing absorption of moisture by the carbon cause resistors to be produced of varying ohmic value. a It is an object of this invention to provide a resistor whose resistance will remain. constant.

The disadvantages residing in the use of sprayed carbon solutions can be avoided by employing solutions containing metal .1nstead of carbon. Solutions of this sort may be the platinum and gold solutions known from the ceramic arts, the precious metal being separated therefrom upon increase of temperature.

According to the is made of solutions ing the desired resistance value. tions by spraying or a fine mist are brought upon the bodies by deposition or recipitation, the-latter being simultaneous y or subsequently heated. Particularly suited for this purpose is esthaves platinum solution. he latter can be used for atomization by the usual atomizers as well as for dividing the solution in the form of a fine mist. The difference betweeen sprayin and the latter procedure. consists in that t e latter is produced by subpresent invention, use ofthis klnd 1n producmitti'ng the solutions to a vfar higher pressure than the pressure employed vfor sprayin su e, the individual droplets become of such small size that they are capable of floating in the air. The same method is in vogue, for instance, in medicine for the purpose of atomizing liquids in suchfine state of subdivision that they can be inhaled in the form at a mist.

In connection with The soludivision in the form of,

Indeed, by application of high pres-.

the manufacture of 1927, Serial No. 161,504, and in Germany February 13, 1926.

highand low-ohmic resistances, high-pressure atomization is particularly suited with the use of liquid solutions of precious metals. On account of the extreme minuteness of the droplets of liquid produced by highpressure atomization, an extremely thin and uniform coat or film of the insulatin supporting bodies. provided with connecting terminals is produced. ltesistances thus made, as regards their appearance, entirely resemble layers obtained by cathodic disintegration or spattering of metals.

,In the accompanying drawing I have shown in Figure 1, to an enlarged scale, 9.

carrier before the deposition of the metallic liqp id solution and,

igure 2 shows, also to an enlarged scale, a completed resistor after the deposition of the metallic resistance solution.

For further details, the method ofmaking the resistors may be described in the following manner: A relatively large number of insulating resistance supports (see' Figure 1), for instance, short glass sticks l-having lead-ins 2 fastened at their ends are placed in highly heated state into a space in which the precious metal solutionsubjected to highpressure atomization is located. According to the length of time for which the resistance supports are kept inside said space containing atomized metal, will a more or less thick film or metallic depositof conducting properties be formed upon the stick.

The process can be applied also in inverse order in so far as the sticks 1 can be placed in the atomizing space in cold state and are then heated after a film of definite nature has formed thereon, the metal becoming incidentally separated. The heating may then be discontlnued after the desired resistance value has been reached.

The method can also be used in combination with automatic apparatus adapted for surface spraying of insulating supports with precious metal solutions. In such. an apparatus, the resistance supports are preferably arranged upon a rotating disk the said supports being periodically conveyed into another space in which they are heated. Later they are again brought for a short while through the spray or the atomizer space where another transient deposit is formed. Since in this method, small quantities of precipitation are alternately formed and separated by heating, it is an easy thingto insure definite and prescribed resistance values in a relatively large number of similarly formed resistance bodies by means of a large-scale manufacturing method. The' resistances thus made are very insensitive to molst-u're and other agencies. Hence, they can be enclosed without the use of any other confinement in a vacuum where their permanent and invariable state is insured.

Instead of the said precious-metal solutions, of course, any other metallic solution made from base metals can be employed, provided they are suitable for the spray or highpressure atomizing ln'oceSsCS.

Having thus described my invention What I claim is:

1. The method of making a resistor having a high resistance of constant value which Consists in'=heating a non-conductive carrier, subjecting, a noble metal solution to a pressure suflicient to form a fine mist thereof, and

directing. said mist over the surface of said carrier/whereby a thin, uniform film of said metal is deposited on said carrier.

2,. A method of making a resistor having a high resistance of constant value which consists in heating a non-conductive carrier, subjecting a solution of a metal, non-oxidizeble at high temperatures, to atomization, and directing the atomized solution over the surface of said carrier whereby a thin, uniform film of said me a1 is deposited on said carrier. v

3. A method of making a resistor having a high resistance of constant value which consists in heating a non-conductive car 'ier, subjecting a platinum solution to. a pressure suflicient to form a fine mist thereof, and directing said mist over the surface of said carrier whereby a. thin, uniform film of platinum is deposited on said carrier.

1 SIEGMUN D LOEWE. 

